Code No.31 A/C (serial message)


caution
  • If diagnosis code No.31 is set in the centre display unit, diagnose the CAN main bus line.
  • Whenever the centre display unit is replaced, ensure that the communication circuit is normal.






TROUBLE JUDGMENT
The centre display unit receives the ambient temperature information signal from A/C-ECU via serial communication. If failure information is sent to the ambient temperature information signal, diagnosis code No. 31 will be set.

PROBABLE CAUSES

  • Damaged harness wires and connectors
  • Malfunction of A/C-ECU
  • Malfunction of centre display unit

DIAGNOSIS PROCEDURE

STEP 1. Check the heater and A/C system.


Check whether the heater and A/C system works normally.

Q. Is the check result normal?
Go to Step 2.
Troubleshooting the heater and A/C system (Refer to GROUP 55 - Troubleshooting ).

STEP 2. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result satisfactory?
Go to Step 3.
Repair the CAN bus lines (Refer to GROUP 54D - Troubleshooting ). Repair the CAN bus line and go to Step 3.

STEP 3. M.U.T.-III other system diagnosis code
Check that the A/C-ECU sets a diagnosis code.

Q. Is the diagnosis code set?
Diagnose the A/C-ECU (Refer to GROUP 55 - Troubleshooting ).
Go to Step 4.

STEP 4. Connector check: D-08 A/C-ECU connector, D-106 centre display unit connector

Q. Is the check result normal?
Go to Step 5.
Repair the defective connector.

STEP 5. Check the wiring harness between D-08 A/C-ECU connector terminal No.32 and D-106 centre display unit connector terminal No.11.

  • Check the communication line for open and short circuit.

Q. Is the check result normal?
Go to Step 6.
Repair the wiring harness.

STEP 6. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)
caution It takes one minute until diagnosis code is detected.
On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code set?
Replace the A/C-ECU temporarily and go to Step 7.
The diagnosis is complete.

STEP 7. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn the ignition switch to "ON" position.
(3)
caution It takes one minute until diagnosis code is detected.
On completion, check that the diagnosis code is not reset.

Q. Is the check result normal?
Replace the A/C-ECU.
Replace the centre display unit